1. Field of the Invention
The current invention concerns novel antiinflammatory and antineoplastic 5-deazaaminopterins and 5,10-dideazaaminopterin compounds and their 5 and 10 alkyl analogs. In particular, the invention concerns 5-alkyl and heteroaroyl-5-deazaaminopterins and 5,10-dideazaaminopterins having antiinflammatory, antileukemic and antitumorigenic biological activity, as well as a method for treatment of inflammatory diseases, leukemia and tumors, pharmaceutical compositions and a process for preparation of these compounds.
2. Background of the Invention and Related Disclosures
Rheumatoid arthritis, malignant tumors and leukemia are severely debilitating diseases which are often fatal, as in cases of leukemia and malignant growths. Drugs which are currently available and used for treatment of these diseases typically have undesirable secondary symptoms or are highly toxic.
Rheumatoid arthritis is one of a number of forms of proliferative diseases. The development of drugs for amelioration or curing the disease has become of primary interest for many years. Until most recently such attempts were without appreciable success.
Rheumatoid arthritis is an inflammation of the joints arising from infectious, metabolic, or constitutional causes, usually of unknown origin. In its advanced stage it is debilitating, as it can result in serious restriction and impairment of movement and even in invalidism. Since rheumatoid arthritis is a common disease that affects 2-3 million people in the United States alone, it poses a serious health problem. With disease progression, a substantial proportion of affected individuals develop erosive joint disease and, despite therapies including disease-modifying antirheumatic drugs such as gold complexes, penicillamine and antimalarials often require surgical joint replacement. In some patients with intractable rheumatoid arthritis, administration of immunosuppressive agents including azathioprine, methotrexate, cyclophosphamide, and combinations of these drugs have been proven beneficial. However, the actual or potential side effects of some of these drugs, including bone marrow toxicity and neoplasia, have limited the frequency and the dose at which they can be administered.
Leukemia is an acute or chronic disease of unknown cause which is characterized by malignant neoplasm of the blood forming tissues in man and other warm-blooded animals. It is characterized by an abnormal increase in the number of immature leukocytes in the tissues of the body and in the circulating blood. The disease apparently affects the blood-forming organs, and is classified according to the type of leukocyte that is being proliferated abnormally. The disease is one of a number of forms of neoplastic disease, and the development of drugs for amelioration or curing the disease has been of great interest. Today, many forms of leukemia can be effectively treated with various drugs. In the case of combination chemotherapy with acute lymphocytic leukemia in children, a large percentage, of five year or longer survivals are obtained. The disease is now classified as curable. However, both the drugs or chemotherapy have very undesirable and debilitating effects and severe secondary symptoms on patients. Therefore, it would be highly advantageous to provide drugs or therapies which would avoid these secondary symptoms.
Malignant tumors typically result from a cellular malignancy whose unique characteristics--loss of normal cellular controls and regulations--results in unregulated growth, lack of differentiation, and ability to invade local tissues and metastasize.
There is no effective treatment of malignant growths aside from radical surgery. Moreover, once the tumor metastasizes, the only therapies which are somewhat effective are radiotherapy and chemotherapy. Both these therapies have severe side-effects which makes the recovery of the patients lengthy, complicated and overall very unpleasant.
It would thus be extremely useful to provide therapies for rheumatoid arthritis, leukemia and malignant tumors with drugs which would be less toxic and still be effective in treatment of these diseases.
The antifolic acid drug, methotrexate, has been used as an antitumor agent since 1955. Its cytotoxic action in tumors is related to its ability to inhibit, essentially irreversibly, the key enzyme, dihydrofolate reductase, required for biosynthesis of tetrahydrofolic acid. Tetrahydrofolate is a vital component in one-carbon metabolism in cells, being required for biosynthesis of purine and pyrimidine nucleosides of the DNA and RNA. Methotrexate is a powerful cytotoxic agent whose principal toxicities affect liver, kidney, and mucosal tissue. Liver toxicity particularly is the paramount concern for use of methotrexate in therapy of chronic diseases such as rheumatoid arthritis.
In 1974, J. Med. Chem., 17:552 (1974) reported the synthesis and antifolate activity of 10-deazaaminopterin. The antimicrobial and antitumor activities of the powerful dihydrofolic reductase inhibitors aminopterin and its N-10-methyl derivative, methotrexate, are well known, and numerous attempts were made to prepare analogues having the improved potency, cell penetration and toxicity properties.
J. Med. Chem., 25: 877-880 (1982), discloses a preparation of N-10 propyl, octyl, and propargyl analogues of methotrexate. Biological evaluations of the three compounds consisted of studies of their effects on inhibition of dihydrofolate reductase and thymidylate synthase, on L1210 cell growth inhibition, on cellular membrane transport with various murine cell types on in vivo activity in mice v. in vitro activity on L1210 leukemia and S180 ascites, and on plasma clearance in mice.
In 1983, J. Org. Chem., 48:4852-4860 (1983) reported that L-5-deazaaminopterin in vitro is equipotent with methotrexate both as an inhibitor of bovine liver dihydrofolate reductase and of L1210 murine leukemia cells and in vivo both against L1210 and P388 leukemia in BDF.sub.1 mice.
The preparation of 10-alkyl-8,10-dideazaaminopterin compounds as potential antitumor agents was described in J. Med. Chem., 27: 376 (1984) and U.S. Pat. No. 4,460,591. While the process described there was useful in the synthesis of certain 10-alkyl-8,10-dideazaaminopterin analogs, it is not suitable for preparation of compounds where the 10-substituent is alkenyl or alkynyl and where a different pterin ring moiety is present (i.e., 2,4-diaminopteridine, 2,4-diamino-5-deazapteridine, etc.), or where the benzoate moiety is replaced by heteroaryl groups. The process generally lacks reproducibility and gives poor yields of impure products in the cyanide-mediated decarbomethoxylation step.
The ability of methotrexate to affect the inflammatory conditions of rheumatoid arthritis may be linked to its cytotoxic behavior. This may be in the nature of immune suppression and could involve attack on inflammatory phagocytic cells such as macrophages or neutrophils and T-helper cells in the synovial region. Very few methotrexate analogues have been evaluated against arthritis in animals, and there is no clear indication whether the antiarthritic properties of methotrexate are directly proportional to its cytotoxicity. Studies published in Chem. Biol. Pteridines, 847 (1986) DeGruyter, Berlin, N.Y. showed that adjuvant arthritis and streptococcal cell wall arthritis in rats responded to doses of methotrexate which were in good correlation to those used in man for treatment of rheumatoid arthritis and that timing and dosage were both important for reduction of inflammation. Both methotrexate and aminopterin were found to inhibit inflammation, but other antifolate compounds that did not possess a 2,4-diaminopyrimidine unit or a benzoylglutamate side chain were found ineffective.
U.S. Pat. No. 4,369,319, discloses 10-deazaaminopterin compounds possessing biological activity against leukemia as well as against other malignancies, including ascitic tumors in warm-blooded lower animals by the administration of 10-deazaaminopterin. The use of deazaaminopterin as antirheumaticum is described in the use patent 5,030,634. The sole compound described in the '634 patent is identical to the compound wherein both R.sub.1 and R.sub.2 are hydrogens described in U.S. Pat. No. 4,369,319.
Other derivatives of methotrexate, namely pyrido[2,3-] pyrimidines, disclosed in U.S. Pat. No. 5,026,851 were found to be active against neoplastic growth. The process to prepare these compounds is disclosed in the U.S. Pat. No. 4,988,813.
J. Med. Chem., 29:1080-1087 (1986) describes a study indicating that modifications at the 5-and 10-positions of classical folic acid antimetabolites lead to compounds with favorable differential membrane transport in tumor versus normal proliferative tissue. J. Heterocyclic Chem., 88:1 (1986), describes the synthesis of 5,10-dideazaaminopterin by two independent routes. Cancer Research, 49:5686-5691 (1988), describes studies examining a new class of 4-aminofolate analogues modified by an N to C conversion and alkyl substitution at the N-5 position of aminopterin and methotrexate.
Chemistry and Biology of Pteridines, (1989,) Walter de Gruyter & Co., Berlin, N.Y., discloses that modifications at the 5- and 10-positions of the classical antifolate structure have produced agents with antitumor activity superior to that of methotrexate. J. Med. Chem., 83:678 (1990), reported the synthesis of the 10-methyl and 10-ethyl analogues of 5,10-dideazatetrahydrofolic acid (DDTHF), a potent inhibitor of glycinamide riboside (GAR) formyltransferase.
It is therefore a primary object of this invention to provide nontoxic but highly effective compounds for treatment of inflammatory diseases, such as rheumatoid arthritis, as well as an effective treatment and inhibition of malignant neoplasms of the blood forming tissues and effective inhibition of growth of malignant tumors with compounds which exhibit relatively low or no toxicity, compared to currently available drugs and treatments.
All references cited herein and in the following text are hereby incorporated by reference in their entirety.